Telephone system



Oct. 11, 1932. G. v. KING ET AL 1,881,669

TELEPHONE SYSTEM Filed Feb. 24, 1951 5 Sheets-Sheet l IIHI- HI ATTORNEY Qct. 11, 1932. G. v. KING ET AL TELEPHONE SYSTEM 1 Filed Feb. 24, 1931 5 Sheets-Sheet 2 G.|/.Kl/VG INVENTORS. EA'BONOM/ A TTOPNE Y Oct. 11, 1932. G. v. KING ET AL 1,881,669

TELEPHONE SYSTEM Filed Feb. 24, 1931 5 Sheets-Sheet 5 a. v. K/N/c MEMO? FA. BONOM/ A TTORNE Y Oct. 11, 1932. G. v. KING ET AL 1,881,669

TELEPHONE SYSTEM Filed Feb. 24, 1931 5 Sheets-Sheet 4 FIG. 5

5: GMK/NG FABONOM/ IN VE N TOR ATTORNEY Oct. 11, 1932. G. v. KING ET AL 1,881,669

TELEPHONE SYSTEM Filed Feb. 24, 1951 5 Sheets-Sheet 5 0L 1 KING FABONOM/ A T TORNE V IIVVENTORS:

Patented Oct. 11, 1932 uni-T a GERALD V. KING AND FELIX A. BONOMI, OF ST. ALBANS, NEW YORK, ASSIGNORS TO BELL TELEPHONE LABORATORIES, INCORPORATED, 015' NEW YORK, N. Y., A CORPO- RATION OF NEW YORK TELEPHONE SYSTEM Application filed February 24, 1931. Serial No. 517,688.

This application relates to telephone systems and particularly to private branch exchange systems and its object is to improve and simplify the service in systems of this character.

, Exchanges of this kind are frequently provided with subscribers lines, trunks leading to other exchanges, tie lines leading to other private branch exchanges, cord circuits for interconnecting subscribers lines and extending connections to other exchanges, and automatic switches for extending connections from other exchanges to subscribers lines in the private branch exchange.

A feature of this invention is an arrangement whereby a signal, in a trunk used for extending connections to and from a distant exchange, is made to flash if the calling subscriber in the private branch'exchange removes the receiver torecall the trunk while the cord circuit of the private branch exchange is still remaining in the answering jack of this trunk; g

Anotherfeature of this invention is an arrangement whereby a holding bridge is removed from a tie line connected to a cord 7 circuit while dialing is taking place and replaced between the seriesof impulses and whereby a ground is maintained on the sleeve circuit regardless of these actions during the dialing operation. The arrangement is such thatwhen the tie line is connected to the cord circuit'a bridge is put across the out going end of the tie line to signal the disthe sleeve circuit. Then when the operator actuates her dial, the sleeve relay is released to cause the bridge to be removed and the tieline to be connected through for dialing, and a relay normally in the bridge is then connected in series with thetip connection for maintaining the ground connection on the sleeve circuit during dialing.

Another feature of this invention is an arrangement in a tieline seizable at a distant exchange and connected to an incoming selector at the private branch exchange whereby a path is provided from the ring 0011- ductor of the incoming selector to the tip conductor of the tie line for a dial tone tant exchange and aground is provided on that may be applied on this ring conductor to notify the distant operator that dialing may take place, and whereby this path may be opened during dialing.

The invention has been illustrated in the accompanying drawings which may be arranged according toFig. 7.

Fig. 1 shows a calling subscribers line in diagrammatic form and a cord circuit at a private branch exchange;

Fig. 2 shows an operators telephone set that may be associated with the cord circuit shown in Fig. 1; 1 Fig. 3 shows a called subscribers line in diagrammatic form terminating in a jack at the private branch exchange;

Fig. 4 shows the circuit arrangement of a tie line and the terminating jack at the private branch exchange;

Fig. 5 shows a, trunk terminating in a jack at a private branch exchange and in diagrammatic form a subscribers line at a-distant exchange having access to said trunk; while Fig. 6 shows the circuit arrangement of another tie line terminating at the private branch exchange in a jack, in the circuit of an outgoing selector and in terminals of an outgoing selector.

To bring out the various features of the invention the following descriptions will be made. First, a call from the subscribers line at 1 through the cord circuit A to the called subscribers line shown in Fig. 3, and recalls from the calling subscriber and the called subscriber before the connection through the cord circuit has been released. Second, a call from the subscribers line at 1 through cord circuit A over'the tie line shown in Fig. 4

to a distant exchange withthe operator dialing the desired subscribers number. Third, a call for a subscribers line in the private branch exchange incoming over the trunk shown in Fig. 5 from a distant exchange and a recall on this trunk from the distant exchange before the connection is released and fourth, a call incoming over the tie line shown in Fig. 6 to a selector 600.

In establishing. a connection from the calling subscriber at 1 this subscriber removes his receiver from its switchhook and causes {i165 The operato'rnow establishes a talking con-' the energization of the usual line relay, not shown, which in turn causes the illumination of the usual line lamp, not shown. lure- V sponse to thissignal the operator in charge of the cord circuit A then. inserts plug 100 into jack 101 thus completing a circuit for the. operation o1 relays 102 and 103 asjfollows: battery,windings'of relays 103 and 102,-sleeve terminals of plug 100 and jack 101 to ground. While relay 103 performs no use- 'ful function in this type of connection it may i be explained here that this cord circuit may be used in other circuit connections where battery will not befurnished in the cord circuit but Where the-connection is cut through directly without any battery or other encumbrances. =ln such cases the marginal relay 102 or 120 is not operated due to a larger resistance in the sleeve circuit of an associated in such cases close a c rcuit for relay 104 and line; Hencerelay 103, for example, would this relay would in turn close an obvious circuit for relay 107. In case the resistance is high in the sleeve circuit of the line associted with the plug 117 and marginal relay 120-thereby prevented from operating, the

the tip an'd ring conductors directly without any batterybetween the "twoplugs. i In such cases certain temporary bridges also-have to be providedf'and these are controlled'by the operation of relay 104- or 120.] For further i'llustrationol the function of-the cord cir-' cuit under these circumstances, reference may be had to our copending application, Serial No. 405,603,'filed November8,1929, and re- "newed June 6, 1931. In'the' present case it 7 fis to benoted that relay 102 in'operating preyents relay 104 from operating by opening thefcircuit for this relay atits lower inner armature and-back contact, closed at the armature and frontcontact'of relay 103 on its.

Yoperation. Relays105 "and106' are also operated through thecircuit completed through i the subscribers loop as follows: battery, one

windi oi relay 106, upper outer armature V fandback contact of relay 107 ,left hand winding of relay 105, contacts of ringingkey 108,

' "tip terminals of plug 100 and']' ack 101 through the subscribers loop back through the-ringing terminals of a'ck101 and plug 100, contacts of ringing key 108, right handwinding of relayl05, lower outer armature and'back "contactof relay 107 and another winding of ;relay 106t0 ground. Relay 106 in operat 1 ing performs no useful functionat this time. Belay 105 in operatingopensat its armature and back contact thegcircuit for supervisory lamp"110 to prevent it from lighting at this time,"

nection with the calling subscriber by operat ing the talking and dialing key 11 1. .21 connectlon is thereby established between the talking conductors of'thecord and the operators telephone set at 200 as follows From the calling subscribers set, tip terminals of jack 101 and plug 100, contacts of key 108, left hand. winding of relay 105, upper outer armature andback contacts of relay 107, condenser 112, 'upper'inner armature and back contacts of relay 10,7, innerniadecontacts of key 111, conductor 113, upper make beforebreak contacts of relay 201, upper inner arinature'and back contact of relay 202, windings of the induction coil 203, condenser 20%, lower out-er armature and back contact 7 of relay 102, lower niake-before-break contacts of relay201, conductor 11%, inner lower made contactsof key 111, lower innerarinature and back contact'ot'relay 107, condenser 115, low-v er outer armature and back contact of relay 107, righthand winding ofrelay 105, contacts of key 107, ringterininalsoi'plug 100 and jack 101 back to the subscribers set at 1. The operators receiver is bridged across the winding ofthe induction coil 203, while the transmitter is inductively connected through induction coil 203 to the above mentioned circuit for the calling subsciibers line.- The callingsubscribers talking battery is sup plied through thewindings of relay 106 and the operators through the windings of relay The operator now challenges. the calling subscriber and learning that a connection is desired to a 'subscribefs station such as isshown' in Fig. 3 and makes the usual busy test by touching the tip of plug 117to the sleeve of jack 300. If the called subs'cribers line is-idle a ground connection will found on the sleeve of jack'300 and no busy indication will be given to the operator. If, how

ever, this line is busy a battery potential will be found on the sleeve of "jack. 300 which willbe connected over'the tip of the plug 117,

upper outer armature and back contact ofre- 300 and a circuit will be closed for the operationof relays 120 and 121 as follows: battery, windings of relays 121 and 120'in series, sleeve terminals-of plug 117 and jack 300 to ground. Relay 121 in operating closes a circuit for the-operation of relay 118 from battery, armature and ,front contacts of relay 121,winding of relay 118 to ground. Relay 121 also closesa circuit for the operation of ,ture and front contact of relay 106, lower outrelay 123 from battery, armature and front contact of relay 121, lower winding of relay 123, outer lower armature and back contact of relay 124, armature andfront contact of relay 105 through a resistance to ground. Relay 120 in operating prevents relay 107 from operatin by opening the connection through its upper-outer armature and back contact fora-circuit otherwise completed for relay 107 at the upper inner armature and front contact of relay 118 when it operates. Relay 120 also causes relay 125 ,to operate as follows: battery, armature front contact of relay 121, upper inner armature and front contact of relay 120, lowerouter armature and back contact of relay 126, windingof relay 125, upper outer armature and front contact of relay 102 to ground. Relay 120 also causes the supervisory lamp 127 to be lighted over a circuit from battery through this lamp, lower outer armature and front contact of relay 120, upper inner armature and front contactof relay 102, lower armature and back con act of relay 128, armature and back contact of relay 129, through a resistance to ground. Relay 120-also opens at one point a bridge across the tip and ring conductors closed at another point by the operation of relay 118. This bridge may be traced froni'thetip conductor of the cord through the lower inner armature and front Contact of relay 118, lower inner armature andback contact of relay 120,-upper outer armature and back contact of relay 104, armaer armature and back contact of relay 104 to he ring conductor. Belay '118 in operating opens the busy test connection through lead 119 at its upper outer armature and back contact and connects the tip and ring conductors of the cord through to relay 125. Relay 118 also opens the connection from battery, resistance 133 to thering terminal of plug 117. Relay 123 in operating provides a locking circuit for itself through its upper winding, upper inner armature and front contact toground at the upper'outer armature and front contact of relay 102 and connects condenser 134 at its lower outerarmature and front contact to the tip conductor across the opening thereinat the lower armature and back contact of relay 125. The lighting of the supervisory lamp 127 indicates that the called subscriber has-not yet removed his receiver from its hook.

' The operation of relay 125clisconnects the plug 117 from the tip and ring conductors of cord A 1d connects at its upper and lower inner armatures and frontcontacts ringing current from a source, not shown, but connected to conductors 136, through the tripping relay 137 and the tip and ring conductors of plug 117 and Jack 800 to the subshown In Fig. 3. Ringing tone is transmitted back to the calling subscribers station through condenser 134:.

V7 hen the subscriber of the line shown in Fig. 3 answers this call by removing his receiver from tie switchhook the tripping relay 137 will operate in the usual manner. This relay in operating removes the short circuit established through its armature and back contact to ground for the lower winding of relay 126 which is thereby permitted to opcrate over a circuit as follows: battery, armature and front contact of relay 121, upper inner armature and a front contact of relay 120, resistance 189, lower winding of relay 126 to ground. Relay 126 in operating opens the circuit for relay 125 which in releasing disconnects ringing current from the line and short-circuits the condenser 13 1. The relay 129 is also operated by the release of relay 125 at this time over a circuit from battery through one winding of relay 129, upper inner a mature and back contact of relay 107, inner upper inner normal contacts of key 111, ringing key 140, upper armature and back contact of relay 125, upper outer armature and front contact of relay 118, tip terminals of plug 117 and jack 300 through the called subscribers loop, ring terminals of jack 300 and plug 117, lower outer armature and front contact of relay 118, lower inner armature and back contact of relay 125, ringing key 1&0, inner lower normal contacts of key 111, lower inner armature and back contact of relay 107, the other finding of relay 129 to ground. Relay 129 in operating opens the circuit for the supervisor-y lamp 120' which is thereby extinguished to indicate to the operator that the called subscriber had answered the call. Relay 129 also closes a circuit for the operation of relay 128 as follows: battery, armature and front contact of relay 121, inner upper armature and a front contact of relay 120, upper winding of relay 128, lower armature and back contact of relay 142, armature and front contact of relay 120 through a resistance to ground. Relay 128 provides a locking circuit for itself from battery at the armature and front contact of relay 121, upper inner armature and a front contact of relay 120, lower outer no-rnial contacts of key 111, lower winding of relay 128, upper inner armature and front contact of this relay to ground at the upper armature and back contact of relay 14A. Relay 128 in operating provides an operating path at its lower armature and front contact for relay 142. This circuit will be described later. Conversation may now begin.

hen the subscriber at the calling station replaces his receiver on the switchhook relays 105 and 106 are released causing the operation of relay as follows: battery, up-

per armature and front contact of relay 121.

upper inner armature and front contact of relay120, lower outer normal contacts of key 111, winding of relay 124, upper make-before-break contacts of this relay, lower in- -ner armatureand front contact of relay 123,

armature andzback contact" of relay 105 through. a resistance to ground; Relay 124 in operating provides a' locking circuit for itself throughits upper inner armature and front contact of relay 102, upper outer armae signal tothe operator.

front contact to the ground at the upper outer armature and. front contact of, relay 102.

Belay 124 closesa. circuit for the lighting of the supervisory lamp; 110. from battery throu h this lamp lower outer armature and ture and, front contact ofrelay' 124 through a resistance to ground. atrelay 105. The lighting of thisiamp serves asa. disconnect When thesubscriber atthe called station replaces his recelver on the switchhook relay 129 is released which causes the operation of a relay 142 over a circuit as follows: bat,-

tery, armature and front contact of relay 121, upper inner armature and front contact of relay 120, lower outer normal contacts of key a 111, winding of relay 142, upper make-beforev 1 ture and back contact of relay 129 through 1 break contacts of relay 142, lower armature and front contact of relay 128, lower armaa resistance to ground. Belay 142 in operating closesa circuit for the supervisory lamp 127 from battery through this lamp, lower outer armature and front contact of relay 120, upper inner armature .andfront contact of relay 102, upper inner armature and front contact of relay 142, through a resistance to ground at relay 129. The lighting of signal 127 serves as a disconnect signal to the operator. Then the plugs 100 and 117 are removed from the jacks 101 and 300 respective ly'all relays remaining operated are released described and when relay 105againoperates lamp 110 is connected to an interrupter cirjcuit as follows: from battery through this lamp, lower outer armature-and front contact of relay 102, upper outer armatureand front contact of relay 124, through a resistance to ground at the armature of relay 105, but as'relay 105 is operated a circuit is also completed through the armature of this relay and its front contact to the lower outer armature and front contact of, relay 124 to an. interrupter; 146 to battery. The lamp 110is thereby alternately short-circuited by thebattery through the interrupter 140 and caused to be alternately lighted and extinguished to serve as an indication that the calling subscriber desires to recall the operator. The operator then actuates the talking and dial key 111 which opens the locking circuithereinbefore described for relay 124 which 'is' thereby released. Relay 124 in releasing discontinues the'fiashing of the lamp 110 under control of the interrupter 146. .The operation of key llliconnects'as heretofore described the operators telephone set with a calling subscribers line.

If the called subscriber desires to recall the operatorhe will alternately operate and release the switchhook and thereby cause the operation and release of relay 129. Relay 129 in releasing causes the operation of relay 142'as hereinbefore described and in operatlng completes a circuit for the supervisory lamp 127 through the interrupter 146 to battery as follows: battery, lamp 127, lower outor armature and'front contact of relay 120, upper inner armature and frontcontact of relay 102, upp'erinner armature and front contact of relay 142 through a resistance to ground at the armature of. relay 129. As this armature is now actuated a short circuit for the battery through lamp 127 wil be provided through this armature and front contact through the lower armature and front contact of relay 142, interrupter 146 to battery'to cause lamp 127' to be alternately lighted and extinguished to serve as a recall signal for the called subscriber. When .the talking key 111 .is operated to connect the operators telephone set with the subscribers line relay 142 is released'by the opening of the locking circuit. From the foregoing it will be seen that either the calling or the called subscriber may by operating his switchhook cause the corresponding supervisory lamp to flash. for recalling the-operator.

Referring now to a connection from a calling subscriber over'cord A through the tie line circuit shown in Fig.4 to a distant private branch exchange the operator will answer the incoming call from the subscriber at 1 by inserting plug into jack 101 and operate key 111 to obtain the desired number in the manner as hereinbefore described in connection with a call between the subscriber at 1 and the subscribers line shown in'Fig. 3. As the call is intended'for a subscriber at a distant private branch exchange, the operator "will then insert plug 117 into jack 400 of an idle tie line leading to the desired private branch exchange. 7 An idle tie line is indicated by a lighting lamp, such as lamp 401 shown in Fig.

- 4. The circuit for this lamp is obvious. The

immediate effect ofthis connection is the closing of a circuit for the operation of relay 405 as follows battery,.resis tance 133, lower outer armatureand back contact of'relay 118, ring terminals of plug ll7i'and' jack 400, lower armature and back contactof relay 406, upper make-before brea-k contact of relay 407, winding of relay 405 to ground. This relay in operating its lower armature extinguishes supervisory signal 401 to indicate that this tie line has been engaged and by closing a con- .5 nection through'the associated front contact,

. extends the battery connection to the relay corresponding to relay 405 in the next idle tie line as indicated, thereby causing the associated supervisory lamp of this tie line to be lighted.- Relay 405 also closes a bridge across the tip and ring conductors of the tie line from the ring-conductor, upper outer armature and front contact of relay 405, retardation coil 409, Winding of relay 410, lower make-before break contact of relay 411, Winding of relay 412to the tip conductor. T he closing of this bridge causes relays not shown in tne tie line at the distant private branch exchange to function and establish a circuit from battery andground-through the winding of relay 412 to cause it to operate. Relay 412 in operating closes a circuit for the operation of relay 413 which in turn closes a circuit for the operation of relay 414. Relay 414 closes a circuit for the operation of relay 407. Relay 407 opens the circuit for relay 405 but closes a holding circuit for this relay at its upper armature and front contact to battery, through a resistance 416. Relay 407 establishes a con nection to ground at the upper inner makebefore-break contacts for the sleeve circuit through relay 403. Theclosing of this circuit causes the operation of relay 403 in series with relays 121 and 120 over the sleeve circuit from battery, windings of relays 121-and 120, sleeve terminals of plug 117 and jack 400, resistance 402, winding of relay 403 to the above mentioned ground. Relay 403 in operating closes a circuit for the operation of relay 418. This relay provides a locking circuit for itself from battery through its lower winding and lower inner armature and front contact to ground at the upper inner armature and front contact of relay 405. Relay 418 also closes a locking circuit through its lower outer armature and front contact for maintaining relay 407 operated. Relays 121 and 120 in operating close circuits for the operation of relays 18 and 123 as hereinbefore mentioned. Relay 118 disconnectsthe busy test sleeve at its upper outer armature anclvback contact from thetip ofthe plug 117 and opens the connection to battery through resistance 133 for the ring conductor, to open the original operating circuit for relay 405. Relay 418 also connects the tip and ring conductors of the cord through to the plug 117 and the cord circuit functions as hereinbefore described in connectionwith the station to station call to light lamp 127. Relay 125 is operated as usual to apply ringing to the tie line, but as the tie line is not yet cut through to the; distant private branch exchange this ringing will have noefi'ect. g Y y l .WVhen the operator observes that the lamp 127 is lighted as an indication that the circuits at the distant private branch exchange are ready for dialing she will again operate dialing key 111. Relay 144 is thereby operated over an obvious circuit and the purpose thereof will become apparent as the description proceeds. The operator then moves the dial 210 fromnormal and a circuit is thereby completed at the off normal contact of the dial for the operation of relay 202. Relay 202 in operating opens the connection as hereinbefore described from theoperators telephone set 200 over conductors 113 and 114 towards plug 100 at its lower outer armature and back contact. This relay also opens another talking path between the connection towards plug 117 over conductors211 and 213 at its upper inner armature and back contact. Relay 202 further closes a circuit for the operation of relay 216 from battery, windings of this relay, upper outer armature and front contacts of relay 202, off normal contacts of dial 210 to ground. Resistance 217 is also connected across the conductors 213 and 211 through the pulsing contact of dial 210; Relay216 in operating short-circuits resistance 217, closes a circuit for the operation of relay 201 at its inner lower armature and front contact and also a circuit for the operation of relay 220 at its lower outer armature and front contact. The operation of relay 201 closes a circuit for retardation coil 225 in parallel with resistance 217 but at the present this coil is short-circuited by relay 216. Relay 207 al o closes a circuit for the operation of relay 221 at its lower inner armature and front contact, opens the circuit through the tip and ring conductor extending between the plugs 100 and 117 over leads 113 and 211 for the tip and 114 and 213 for the ring conductor leaves the impulse contacts of the dial 210 connected across the conductors 213 and 211 and connects conductors 113 and 114 to the upper and lower outer armatures of relay 224. The complete circuits for the conductors 113 and 114 will be traced later. The circuit for the conductors 213 and 211 may be traced as follows: From conductor 211 through the pulsing contacts of dial 210, upper armature and front contact of relay 216, to conductor 213. Relay 220 in operating provides a locking circuit for the relay 202 through its lower winding. Relay 220 also opens the circuit through its upper armature and back contact for the operators receiver and shortcircuits it at the front contact. Relay 220 being slow in releasing will maintain the receiver short-circuited for a short time after the dial is restored to normal in order to prevent undesirable clicks in the receiver at this time, as well as to prevent the attendant from hearing the transmission of the dial pulses.

Relay 221 in operating performs no useful function at this time.

should be noted that on the operation ofrelay 202 relay-226 vvasoperated, due to theoperation of relay 144,,over acircuit from battery, armature front contact of relay 121,

upperr inner armature and front contact, of

relay 120, upper'vvindin'g of relay 126 and upper make beforehreak contact of this 'r'elay, lower armature and front contact of relay 144, conductor 227, Winding of relay 6' 226, upper outer armature and trout conmeter relay 202 to ground. Relay 225 in operating closes an obvious circuit for the operation of relay 224. The operationof re- 4 day e'224 'closes an obvious circuit through the windings of relay 223 Which is thereby operated." Relay 224 also 'bridgesthe relay 228 Y across the conductors 113 and 114 at its uppeer and lower outer arniatures-and' front contac ts; Battery and ground are furnished at 201 operated. a

this time as will be hereinafter described over conductors 113 and 114 to cause relay 228 to op'erate to provide ajlocking circuit for: relay- 224 to maintain this relay andrelays 223and Referring now. to the operation of the cord circuit'ii and'the-tie line shown in Fig. 4 in} responseto the op eration of the dialing key 111, a circuit is closed-through the upper winding of relay 126 as liereinbe'fore men- 3 ti'oned'gdu to the operation otrelay 202, and to the actuation of the dial 210.; 'Eelay 126 is thereby operated-to closea locking circuit for itself'throughthe resistance 139 audits lower winding. The operation of relay 126 opens the circuit for; the relay 125 Which is thereby released to open the connection irom'the ring- 7 ing source at leads 136 connected to-thetip 4o alsoconnects the sleeve conductor of plug 117;

and ringpconductors over. plug 117 tothe tie ig."4.'- The operation of relay 126 f to the ground" on" conductor 227 applied at 5 a the upper armature'and front contact or" relay 202 through-relay 226. The resistanceof 4 the winding 01? relay'226 is low so as to cause the release of relay 403 in the tie line by short circuiting the battery'on the sleeve circuitin the cord. Relay 403 in releasing causes [the operation of relays 406 and 411 over obvious circuits.- Belay 403 in releasing also closes-at its lower armature andback contact, a bridge across the tip'and ring conductor ofthe line through" conductor 420 and resistance 421't0 aid in pulsing over theline. new 406 inoperating provides a lock ng circuit for itself through its upper armature andfront cone Y tact to'ground at the upper armature and front contact oi relay 418, and connects at the lower armatureand front contact ring conductor to the lowerarniatureofrelay 411. 7 ;Relay 406 in conjunction with relay 41 1 di-sof thealine and relay-$411111 operatingdise connects. the tip-V and ring conductors 4mm the condensers 423 andi424 and connectsthe connects the bridge 3 consisting of the relays 410 and 412 fromv the tip and ring conductor Vvvithout encumbrances.

tip i'coiiductor through the vvinding of relay 412 to the distant private branch exchange and thering conductorf directly through- V by maintained operated.

' Dialpulses are now transmitted on-theYrea turnot the dial. During the pulsing the relay 412 may release and reoperate following the dialing pulses. *Hovvever, on account'of the sloW'-to-release characteristics of relays 418 and 414the ground connection established by relay 407 for the sleeve circuit of jack 400 Will be maintained during pulsing, "When the dial returns ,to-normal .relayl 403 will reoperate due to the release or" relay'202' 'asxvill hereinafter be described, and relay 412 Will be inaintained'operated While-relay 411 Willrelease between series; This'se-fquence of operation and release of relays 4'03 and 411' is'repeated' until the complete number has been dialed. Thus it Will'be'se en that the ground connection to the slee've Will be maintai'ned' durin ulsin While the bridge through relays 410 -and412 Will'be restored-across thetip and'ifing conductors between" the series :01 v impulses to maintain the proper circuit cond tions at the distantend of the tie line.

-Vl hen' the dial has returned to normah after. a series of impulses has beentransmitted relay 216 is release d.'?l1his relay in releasing removes the short 01131111: from the parallel combination 217 and'retardation coil 225and also causesth'e release of therelay' 220. The release of-rela-y 220 reinoves the Relay 412 is thereshort circuit hem theFoperators telephone setand causes the release :of relay 202 as the original c rcuit for th srelay is opened on there-turn of the dial to normal; ,The release of relay202 removes the sliuntthrough the resistance 217'for the bridge through the retardation coil225. The retardation coil 225' 7 now holds the connection established'over the tip and ring conductors between the seri'es of impulses. The releaseofrelay 202 causes, as f hereinbefore stated, thereoperation of relay 403 ith the consequent insertion of; the.

bridge across the outgoing end ofthe tiee line in Fig. 4; 'VVhen all the digits have been dialed the key 111is restoredcausing relays 223; 201, 221, 22s and 22 i to release Relay 22Ijbeing sloW in releasing will keep. th e' 'receiver circuit iopen longenough toprevent a 0110]; through the operators receiver due to the release of thetalking'ckey.

:The called subscriber is thenrung-in the usual manner and in response thereto removes his receiver from the s'vvitchhook, 5 Relay410 is tli'ereby operated due to a reversal of the current on the line from the distant ex:

change;- This relay in operating-causesthe operation of-jrelay V4261andrelay 426 removes ashort circuit from the retardation coil 409 in" the bridge consisting of the relays .412

and, 410 to include thiscoil in the bridge;

Relay 426 in operating also connects the retardation coil 427 across the tip and ring conductor towards the jack 400 to cause the operation of relay 129, which in turn causes the operation of relay 128. Relay 128 in operating causes the lamp 127 to be extinguished as a signal that the calling subscriber has answered. As hereinbefore described relay 411 releases when relay 403-is reoperated asthe dialing is finished and a talking connection is now completed between the subscribers through condensers 423 and 424andalsothrough condensers 112 and 115, talking battery for the link separated by these two sets of condensers being furnished through the windings of relay 129, talking battery for a the calling subscriber through the windings of relay 106 and talking battery for the called subscriber at the distant exchange. I

r When the receiver, at the called station is replaced on the switchhook, relay 410 will release causing release of relay 426. Relay 426 in releasing causes relay 129 torelease and relay142 to operate. Relay 142 causes the lamp 127 to light, as hereinbefore described, as a disconnect signal. WVhen the plug 117 is removed from jack 400 relay403 will release causing relay 411 to operate. This causes the release of relays 412, 413, 414, 407, 405 and 418. Relay 418in releasing causes 7 the relays 411 and 406 to. release and restore the circuit to normal. Relays 120 and 121 are also released by the removal of plug 117 from jack 400, and this in turn causes the release of relays 142, 128, 124 and 123, and the extinguishing of lamp 127. When the plug 100 is, removed from jack 110, relays 102 and 103 are released.

A description will now be made of a call incoming over trunk 500 shown in Fig. 5, from a subscribers line 501 at a distant exchange for a private branch exchange sub- 502 in operating closes an obvious circuit for the operation of relay 506 which in turn closes an obvious circuit for'the operation of relay 507. Relay 507' in operating causes a ringing tone from'a source connected on relay 508, not

' shown, to be transmitted over-the ring conductor to the distant exchange; The operation of relay 506 closes a circuit for the operation'of relay 504 as follows: from battery, winding of relay 504, lower armature and front contact of'relay 506 to ground at the lower armature and back contact of relay 509. Relay 504 in operating provides a locking circuit for itself through its lower inner armature and front contact to ground under the control of the relay 506. Relay 504 in conjunction with relay 507 closes a circuit for the lighting of the supervisory lamp 511, from battery, upper inner armature and front contact of relay 504, lower outer armature and front contact of relay 507, lamp 511 to ground, to indicate the presence of a call on this trunk. The operator of cord circuit A. answers this call in the usual manner and extends a connection to the desired subscriber. It should be noted that relay 504 in operating establishes a talking connection through the repeating coil 503 at its upper and lower make-b-efore-break contacts and extends the connections for relay 501 through the windings of the repeating coil 503. When the plug 100 is inserted in jack 512 to answer the call relay 509 is operated over the sleeve circuit and this relay closes a circuit for the operation of relay 514 from battery, winding of this relay, upper armature and front contact of relay 509, lower armature and front contact of relay 506 to ground at the lower inner armature and front contact of relay 504. Relay 514 opens the circuit for relay 507 which in releasing removes the ringing tone from the tip conductor of the trunk and extinguishes the lamp 511. Relay 514 in operating provides a locking circuit for itself under control of, relays 504 and 506.

WVhen the trunk is released by the subscriber of line 501 replacing his receiver on branch exchange operator has removed plug" from jack 512, relay 502 will again opcrate, and cause the operation of relays 506 and 507, but due to the operatbn of relay 509, relays 504 and 514 will not operate at this time. A circuit is therefore closed from ground through the lower inner armature and back contact of relay 504, upper outer armature and front contact of relay 507 through a start leadto the winding of relay 516 to battery. Relay 516 operates'to start an interrupter mechanism 517 to establish an interrupted circuit from battery for lead 518. Relay 516 and mechanism 517 may be common to a plurality of trunks. The circuit over lead 518 extends through the upper inner armature and back contact of relay 504, lower outer armature and front contact of relay 507 and lamp 511 to ground so that this lamp will now be alternately lighted and etlav 504 to'o' o'en the'interrn jted battery cir- ;CU.li3'fIOi1Q 518 and also the release of relay 516 to stop the interrupting mechanism; When jack 602 to the distant exchange or automatically through connector switch 60 1. Calls, incoining over-this trunk may be extended anto-- lnatically over the selectorv switch 600 to a de sired subscribers line at the private branch exchange; The automatic switches 60%. and

600rhave only been indicated by boxes as they may be 0t any type well known in the art. To illustrate the feature of this invention relatingtothe transferring of a dialing tone from the ring conductor of the incoming se- V vle-ctor 600-to the tip conductor of the tie line exchange a circuit is established over and ring conductors, upper outer and lower larmatures and back contacts of relay 606, .30

601 a description will be made or" an 111g call. I. When tie line 601 15 selected at a incomdistant windings of relay 60?,winding 3ofrelay 608 to the. tip and ring co-nductorsof the selector 600.- :The selectorwillthen function in a welllrnown manner to apply a connection to ground for the sleeve conductor from the selector. This causes-relay 609 to operate from battery,winding ofrelay 609,.upper inner armature and back contact of relay 606, the sleeve conductor to ground at the selector 600.

' Relay. 609 in operating opens the circuit for lamp 610 associated with'iack 602to extin- "guish it as an indication that line'601 isbusy.

Relay 609 also connects battery to the. lower armature and back contact of the relay cor responding torelay 609 in the next idletie .45

line to light the lamp corresponding to lamp 610 oztsaid tie line toindicate its idle condithe sleeve circuit otthe jacks 602to make this 'tion. Relay 609 also at its upperouter armature and front contact estab ishes a connection to batterythrough a. resistance and, the lower armature and back contact of relay .6l2to jack test busy; A; connection to gronnd is also establishedat the upper inner arr ure and front contact of relay 609 for the sleeve conductor of this tie line terminating in a sleeve terminal atthe connector 604, to make this linev busy for automatic selection. .Be-

lay 607 which operates intliecircuit from the distant exchange opens a branch of the sleeve circuit for relay 61"- to prevent this relay from operating'at the seizure otthe selector 600. When the'selector 600. is ready for the reception 'ofdi-al pulses it will provide adialingtone over its ring'conductor. ThisIto-ne therefore, due to the normal condition of rethe tip 6 distant exchange .asan indication thatjdialinginay begin.

During dialing pulses and relay 614 therefore operates on the-first i1npulse.- Relay 61ljis slow-in relea-sing-soit Will remain operated during dial ingand thereby open the. connection between the tip and ring condnctor to remove thed-ial .tonegv I r When the called station, answers battery and groundfron the incomingselector 600' are reversedto the distant exchange for su-. pervisoryjpurposes and relay'608 which is polarized. operates. Relay 608 in operating closes a circuitl'forthe operation of relay 619' w iich opens (the circuit for relay 614E-as well as the connection coniprising the condenser 617 and resistance 616 between the tipand ring conductors. Belay 619 also short-cin cnits the windings of relay607 and connects the line 601through its arinaturestojselector 600 and the called subscribers line for con.- versation; On disconnection either atthe dis. tant exchange. or at the called snbscrib'ers relay 6Q? iollows the ilnendof the circuit relay 606 is released causing the release ofrelay 2619;; .The ground on the sleeve, of selector 6001s also removed causing the releasejof relay 609. This relay in releasing removes the busy condition'on the sleeve of the aclr 602 and-thesleeve terminal ofthis line at connector 60 1. Relay 609 in releasing relights a lamp to indicate that this line is. now idle. 1 11 m.

3 While'this invention has beenillustrated in connectionv with bat a single system it should be LlIldQI'S-tOOd-illlthiii/11125 readily be. applied to other systems without departing from the spirit thereof. f i a 'l/Vhat is clain edis: 7 v a r v 1.1 In a telephone systenn a'line, a cord circuit, means for "establishing a connection between saidline. and cord circuit, a signalin said l ne an nterrnpting device in said line, 1

line and saidcord circuit through saidtrunk;

assure said signal in response to the seizure of said trunk by said subscribers line, means for disabling said signal in response to the establishing of the connection between said cord circuit and said trunk, and means responsive 'to the abandoning of the connection by'the 'a trunk, a cord circuit, a signal in said trunk,

means for establishing a connection between said subscribers line and said trunk, means responsive to the establishing of said connection for actuating said signal, means for establishing a connection between said cord circuit and said trunk, means responsive to said last mentioned connection for disabling said signal, an interrupter associated with said trunk circuit, and means responsive to the abandoning of the connection by the subscriber and to the reseizing thereof by said subscriber for actuating said signal under control of said interrupting device.

5. In a telephone system, a subscribers line, a trunk, a cord circuit, a signal in said trunk, means responsive to the seizure of said trunk by said subscribers line for actuating said signal in one manner, means responsive to the establishing of connection between said cord circuit and said trunk for disabling said signal, means responsive to the subscriber replacing his receiver on the switchhook and again removing it for actuating said signal in a different manner, means responsive to the removal of said cord circuit from said trunk for changing the operation of said signal from said secondmentioned manner of ating said sleeve relay, means for releasing said relay for removing the bridge and for connecting through the tip and ring conductors of the tie line for direct current dialing, and means for maintaining said ground connection on the sleeve circuit during dialing.

7. In a telephonesystem, a tie line comprising tip and ring conductors and a sleeve circuit, means for connecting a bridge c1rcu1t across the tip and ring conductors of said tie line and for establishing a connection to ground for said sleeve circuit, a relay in said sleeve circuit, means responsive to the establishing of said connection to ground for actuating said relay, means for releasing said relay, means responsive to the release of said relay for removing the bridg'e' 'and for 'je i n tinsth e g t ,t p a ng .01 Tductorsjof the tie line fordirect" current dialanothe'r relay, means responsive to the release of said'first'relay for including said iidfre gay in the tip connection aIld fOI' "said second relay, and means responsive tothe operation of said secondie- I i 1 Y l' l lay for maintaining said connection to ground on'il ie sleeve circuit during dialing over said conductors.

n atelephojne system, a tie line commgtip and conductors and a sleeve sleeve circuit, a sleeve relay in said sleeve circuit, a cord circuit, means responsive to,.

circuit, a relay in said bridge, means responsive to the establishing of the said connection to ground for actuating said sleeve relay, means 1n said cord c1rcu1t for releasing said sleeve relay, means responsive to the release of said sleeve relay for disconnecting said bridge and for establishing connections through the tip and ring conductors for direct current dialing therethrough and for connecting said relay in series with the tip connection, means for operating said relay" during dialing, and means responsive to the operation of said relay for maintaining said ground connection on the sleeve circuit during dialing.

9. In a telephone system, a tie line,

switch, a signaling path between the ring conductor of said switch and the tip conductor of said tie line, and means responsive to impulses received over said t-ie line to activate the switch for removing said signaling" path.

10. In a telephone system, a first exchange, a second exchange, a tie line connecting said exchanges, a switch at said second exchange, having tip and ring conductors conneotable to the tip and ring conductors of the tie line, a signaling path between the ring conductor of the switch and the tip conductor of the tie line, and means responsive to impulses.

incoming over the tie line from the first ex change to actuate the switch for removing said signaling path.

11. In a telephone system, a first exchange, a second exchange, a tie line connecting said.

exchanges, a switch at said second exchange,

a signaling path between the ring conductor of the switch and the tip conductor of the tie line, a relay responsive to the reception of impulses over the tie line to actuate the switch for the opening of said signaling path.

12. In a telephone system, afirst exchange, a second exchange, a tie line connecting said exchanges, a switch at said second exchange, means at said second exchange responsive to,

"impulses ineoming over the tip and ring on i ductors ofthe tie line to said second exchange fer actuating said switch, a slow release re- "lay, meansfor maintaining said relay ope'rated during the transmission of impulses, f and means Operative due to the maintenance pf said i'elay operated during the transmis sion of impulses for opening of said. signala i ing thduring this period.

In witness whereof, We hereunto subscribe (iufnames this th day of'February, 1931.

a v GERALD V. KING.

' FELIX A. BONOMI. 

